As a general rule, a motor vehicle suspension system comprises a suspension strut supporting an axle and a vehicle wheel. A suspension thrust bearing is disposed in the upper portion of the suspension strut, opposite the wheel and the ground, between a suspension spring and an upper support block attached to the body of the vehicle. The suspension thrust bearing includes at least one rolling bearing. The spring is disposed around a shock absorber piston rod, the end of which may be attached to the body of the vehicle.
The suspension thrust bearing therefore enables transmission of axial forces between the spring and the body of the vehicle at the same time as allowing relative angular movement between the rolling bearing cup of the spring, which is mobile in rotation, and the fixed support block attached to the body. This relative angular movement may arise from turning a steerable wheel and/or compression of the suspension spring.
A shock absorber bump stop, for example of rubber or elastomer, is generally mounted around the piston rod of the shock absorber and inserted in a bore in the lower cap and immobilized axially under the suspension thrust bearing.
In the event of a shock to the suspension strut, the spring, the piston rod and the shock absorber bump stop are compressed axially and exert on the suspension thrust bearing a force that can exceed 60 kN. In particular, the shock absorber bump stop transmits an axial force against the suspension thrust bearing and is deformed radially. This radial deformation of the bump stop then exerts radial forces on the lower cap in which it is inserted, which can weaken the area of contact of the bump stop with the lower cap to the point of it breaking.
It is this problem that the invention more particularly intends to address by proposing a new suspension thrust bearing that is simple and economical to manufacture and to assemble at the same time as guaranteeing high resistance of the shock absorber bump stop to transmitted shocks.
To this end, the invention concerns a suspension thrust bearing including at least one rolling bearing forming an axial thrust bearing disposed on a lower cap. The lower cap includes a body with an annular rolling bearing portion for a spring and the tubular portion includes a bore in which a shock absorber bump stop is inserted.
In accordance with the invention, an axial contact surface defined on the lower portion of the bore of the tubular portion against which the shock absorber bump stop when deformed exerts a radial force and the tubular portion includes a reinforcing insert located at the level of this axial contact surface.
Thanks to the invention there is provided a suspension thrust bearing provided with a lower cap that is economical, robust and perfectly able to support forces encountered in normal use and forces caused by shocks transmitted by the shock absorber bump stop to the tubular portion.
The invention makes it possible to avoid having recourse to costly techniques or materials, such as an entirely metal lower cap that does not lend itself well to centering rolling bearing races pressed from thin sheet metal, often of complex shape, and the rolling bearing engagement of which on the cap must be carefully designed and regular in order to avoid deformation and deterioration of the lower race. A metal lower cap also represents an additional cost because of the necessity of applying an anticorrosion treatment to it, for example by cataphoresis.
Moreover, the suspension thrust bearing in accordance with the invention is suited to applications on different types of vehicles generating higher or lower axial and radial forces on the suspension, thereby making it possible to reduce greatly the cost of production of such a thrust bearing in that most of the component parts thereof may be made in one piece in one production operation and only the presence of an insert is specific for applications to very high forces applied in the event of shock.